1. Field of the Invention
The invention relates to an apparatus for generating very high pressures, for example the conversion of graphite to diamonds.
2. The Prior Art
Known apparatus for the generating very high pressures, e.g. known apparatus for conversion of graphite to diamond, have pressure chambers with relatively small volumes. It has long been desirable to achieve high pressure apparatus with a greater volume of the pressure chamber since such apparatus would result in increased capacity. One reason why it has been impossible to realize this desire are the frictional forces generated between the material enclosed in the pressure chamber and the walls of the pressure chamber, as well as in the material itself, when the material is subjected to compression. The frictional forces cause the pressure to decrease successively in a direction towards the interior of the volume of the material and therefore limit the thickness in the direction of compression of the volume material within which it is possible everywhere to attain a certain desirable minimum pressure, that is, they limit the height of the pressure chamber if the compression is assumed to take place in a vertical direction. If a considerably larger volume of the pressure chamber is sought by increasing its area perpendicular to the direction of compression, other problems are encountered. One problem is that the forces which would then be required to generate the pressure are so great that they cannot be overcome under practical conditions. Another problem is that there are no possibilities of manufacturing components for the parts of the high pressure apparatus located nearest the pressure chamber. These components, for example parts of cemented carbide, would be too large to be manufactured with sufficient strength. Regardless of how the pressure is generated, the necessary gaskets must be dimensioned so as to prevent the material from flowing out of the pressure chamber. This requirement limits the thickness of the gaskets.
A high pressure apparatus which is well-known among experts and which has been used when manufacturing diamonds on a commercial scale is described in the U.S. Pat. No. 2,941,248. The apparatus comprises a pair of opposed punches and a die arranged between them with a central throughgoing hole. The two openings of the hole are formed with outwardly increasing cross-sections and each punch with an inwardly decreasing cross-section in a corresponding manner, so that the punches may be inserted into the hole to a certain depth. Between each opening of the hole of the die and each punch there is arranged a gasket which seals the pressure chamber formed of the punches and the hole of the die. This high pressure apparatus, which must be dimensioned for each specific application, has a pressure chamber with a relatively small volume. A modification of the apparatus to increase the volume of the pressure chamber would cause the problems described above.